Nanoscale Zero-valent Iron Particles Research Articles

Transport of nanoscale zero-valent iron in the presence of rhamnolipid

Nanoscale zero-valent iron (nZVI) particles have gained widespread use for in-situ treatment of various chlorinated hydrocarbons. Their non-toxic nature, affordability, and minimal maintenance requirements have made them a favored material for nanoremediation. The treatment typically involves the injection of nZVI particles into contaminated sites using direct-push well injection systems. However, their small size leads to high surface energy, causing aggregation that alters their physiochemical properties, reactivity, and transport behavior. To counteract aggregation, nZVI suspension can be stabilized with different surfactants, reducing the surface energy during subsurface soil transport. This study investigates the impact of rhamnolipid, a biosurfactant produced by Pseudomonas aeruginosa during the late growth phase, on the aggregation and mobility of nZVI particles. The retardation factor of nZVI in the model media of zeolite, ZK406H, decreased from 1.66 in the absence of rhamnolipid to 1.03, 0.98, 0.93, and 0.87, corresponding to the presence of rhamnolipid at concentrations of 20, 50, 80, and 100 mg/L. The deposition coefficient also decreased from 2.39 in the absence of rhamnolipid to 0.459, 0.279, 0.217, and 0.0966, corresponding to the presence of rhamnolipid at concentrations of 20, 50, 80, and 100 mg/L. The transport parameters of nZVI in ZK406H were linked to the interactions of nZVI particles with ZK406H by the DLVO theory.

Nano zero-valent iron/montmorillonite composite for the removal of Cr(VI) from aqueous solutions: Characterization, performance, and mechanistic insights

Infiltration of hexavalent chromium (Cr(VI)) into the human body poses significant health risks, including the risk of developing cancer and increased mortality rates. The discharge of chromium-contaminated wastewater from industrial processes exacerbates environmental pollution, highlighting the necessity for efficient, cost-effective, and environmentally friendly treatment methods. In recent years, there has been a growing emphasis on the application of nanoscale zero-valent iron particles (NZVI) for mitigating Cr(VI) water pollution. In the present study, NZVI was synthesized using a liquid-phase reduction method employing sodium borohydride (NaBH4), and natural montmorillonite (Mt) was incorporated as a carrier, resulting in the creation of NZVI/Mt., a composite material. Characterization of this composite was performed using scanning electron microscopy (SEM), Transmission Electron Microscope (TEM), Specific surface area and pore size (BET), X-ray diffraction (XRD), and Fourier-transform infrared (FT-IR) techniques. The investigation encompassed an exploration of the influence of initial pollutant pH levels, adsorbent dosages, and initial pollutant concentrations on the adsorption process. The research findings indicate that, at an initial pH of 4.0, NZVI/Mt. achieves a removal efficiency of 92.41% for a Cr(VI) solution with an initial concentration of 40 mg/L. The NZVI/Mt. composite adheres to both a pseudo-second-order kinetic model and the Langmuir isotherm model, showcasing a significant maximum adsorption capacity of 67.75 mg/g for Cr(VI). Furthermore, thermodynamic analysis revealed an exothermic nature of the adsorption process. This experimental approach effectively resolved issues related to NZVI particle agglomeration, offering a simplified, cost-effective, and environmentally friendly preparation method. Consequently, the NZVI/Mt. composite material demonstrates effective treatment of Cr(VI) mildly contaminated wastewater.

Method validation of an inductive measurement system (IMS) for nanoscale zero-valent iron (nZVI) particles determination in sand-packed columns

The purpose of this work was to develop and validate a rapid, non-destructive, real-time measurement system for nanoscale zero-valent iron (nZVI) particles determination in sand-packed columns. This aims to provide an approach to analyse for nZVI particle transport and nZVI induced contaminant degradation reactions in 1-dimensional aquifer experiments. The inductive measurement system (IMS) was developed and tested by measuring columns filled with varying portions of nZVI and sandy aquifer material. Method validation was conducted for this innovative approach in accordance with several guidelines in disciplinary areas. The linearity of ZVI concentration and measurement signal was confirmed. Calibration curves were determined to be linear over the range of 0.11–53.50 g/L for nZVI NANOFER STAR, 0.10–81.67 g/L for nZVI BASF 1, 0.12–58.26 g/L for nZVI Carbo-Iron, 0.12–69.70 g/L for nZVI NANOFER 25DS ORM, 0.12–50.69 g/L for nZVI NANOFER 25DS, and 0.21–1613.39 g/L for nZVI Höganäs 1* (dry). This method was determined to be sensitive in nZVI, accurate (101.63 % within-run recovery, 101.85 % between-run recovery covering 76 days), and precise (0.46 % repeatability RSD, 0.85 % intermediate precision RSD covering 76 days). LOQ was determined ranging from 0.10 to 0.21 g/L for nZVI used in experiments and regression through origins was selected as the calibration model. Quality control processes were performed to assure the reliability of the results and the long-term stability. Additional data processing steps allowed to compensate for measurement deviations resulting from different liquid phase compositions, e.g. dispersants used for nZVI suspensions. This method is now successfully validated in single-laboratory conditions.

Exploring the Impact of Surface Functionalization on the Reaction, Magnetophoretic, and Collective Transport Behavior of Nanoscale Zerovalent Iron.

This study provides a systematic analysis of the transport and magnetophoretic behavior of nanoscale zerovalent iron (nZVI) particles, both bare and surface functionalized by poly(ethylene glycol) (PEG) and carboxymethyl cellulose (CMC), after undergoing a chemical reaction. Here, a simple and well-investigated chemical reaction of methyl orange (MO) degradation by nZVI was used as a model reaction system, and the sand column transport and low-gradient magnetophoretic profiles of the nanoparticles were measured before and after the reaction. The results were compared over time and analyzed in the context of extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory to understand the particle interactions involved. The colloidal stability of both bare and functionalized nZVI particles was enhanced after the reaction due to the consumption of metallic Fe content, resulting in a significant drop in their magnetic properties. As a result, they exhibited improved mobility across the sand column and a slower magnetophoretic collection rate compared to the unreacted particles. Here, the colloidal filtration theory (CFT) was employed to analyze the transport behavior of nZVI particles across the packed sand column. It has been observed that the surface properties of the reacted functionalized particles changed, possibly due to the entrapment of degraded products within the polymer adlayer. Moreover, quartz crystal microbalance with dissipation (QCM-D) measurements were performed to reveal the viscoelastic contribution of the adlayer formed by both bare and functionalized nZVI particles after the reaction on influencing their transport behavior across the sand column. Finally, we proposed the implementation of a high-gradient magnetic trap (HGMT) to reduce the transport distance of the colloidally stable CMC-nZVI, both before and after the reaction. This study sheds light on the behavioral changes of iron nanoparticles after the reaction and highlights environmental concerns regarding the presence of reacted nanoparticles.

Sustainable developmental measures for the treatment of pharmaceutical industry effluent using nano zero valent iron technology (nZVI) – A review

Among the diverse nanomaterials, nanoscale zero-valent iron (nZVI) particle is one of the superior materials used for the condition of remediation and environmental restoration. As a result of the nanoscale dimension of nZVI particles and its relatively high surface, it is capable of undergoing various chemical reactions, including reduction, oxidation and adsorption of toxic metals, inorganic substances and organic compounds. In the pharmaceutical industry, mass production of drugs results in the widespread dumping of effluents. As emerging pollutants, antibiotics are non-biodegradable compounds that have potential to adversely affect human genetic and hormonal systems posing a risk to human health and the environment. Global health is endangered by antibiotics present in surface waters and drinking water. Drug contaminants can be removed using a synergistic process involving various advanced methods, including ozonation, fenton process, photocatalytic degradation, reverse osmosis and, adsorption techniques. The enhancement of nZVI composites and earlier studies were reviewed, as well as the evaluation of zero valent iron nanoparticles' effectiveness in eliminating antibiotic effluents from water bodies. This review also revealed the various methods of the determination of toxicity associated with nZVI treated pharmaceutical effluents. The present study would suggest the possible utilization of nZVI technology for the effective removal of hazardous pharmaceutical contaminants through sustainable green measures.

TEMPO oxidized cellulose nanocrystal (TOCNC) scaffolded nanoscale zero-valent iron (nZVI) for enhanced chromium removal

The conventional carboxymethyl cellulose (CMC) stabilization hampered available active sites of adsorption and reduction, due to irregular shape of nanoscale zero-valent iron (nZVI) particles with augmented average size and passivated surface, leading to insufficient removal and poor resistance against complex environmental conditions. Herein, we presented (2,2,6,6-Tetramethylpiperidine-1-oxyl)-mediated (TEMPO-mediated) oxidation of cellulose nanocrystal (TOCNC) scaffolded nZVI (nZVI@TOCNC) with enhanced efficiency for chromium removal in comparison with CMC stabilized nZVI (nZVI@CMC). The anchoring of nZVI at the functional sites of TOCNC was initiated by liquid-phase chemical reduction method. The nZVI@TOCNC showed improved nZVI distribution with uniform particle size and thinner shell (∼1 nm). Characterizations using FT-IR, XPS and XRD demonstrated that bindings between TOCNC and nZVI were through hydrogen bonds, electrostatic attractions, coordination-covalent bonds and bidentate chelation. TOCNC with shorter branch-chain (–COC–) surrounding the nZVI could potentially form a porous and compact “mesh” to rigidly encapsulate nZVI, while CMC wrapped around nZVI in the way of traditional polymeric stabilizers. Thus, 0.5 g/L nZVI@TOCNC achieved 99.96% Cr (Ⅵ) removal efficiency (20 mg/L) at pH = 7 and the removal capacity were up to 55.86 mg/g. The nZVI@TOCNC consistently presented higher removal efficiency than nZVI@CMC under wide pH range (3–7). Cr (Ⅵ) was reduced to Cr (Ⅲ) by nZVI@TOCNC with deposition of CrxFe1-x (OH)3 and Cr2O3. The predominant mechanisms of removal probably consisted of electrostatic attractions, reduction, co-precipitation and surface complexation. The pseudo-second-order kinetic model well-fitted the sorption kinetic, indicating TOCNC scaffold stabilized nZVI for efficient reduction of Cr (Ⅵ) through multi-layer adsorption. As a template and delivery carrier, TOCNC shows promising potential to further improve the capability and practice of nZVI for in situ treatment of industrial waste water with heavy metal pollution.

Improved Delivery of Nanoscale Zero-Valent Iron Particles and Simplified Design Tools for Effective Aquifer Nanoremediation

The subsurface injection of nanoscale zero-valent iron particles (nZVI) for the in situ reductive remediation of contaminated aquifers has grown over the last 25 years. However, several efforts are still being made to improve the stability and delivery of nZVI and to simplify the procedure for site-specific injection design. In this study, the injectability and mobility of a commercial nZVI-based reactive gel was tested in a radial geometry laboratory setup. The gel proved to be highly mobile in sandy porous media, allowing for the achievement of a radius of influence (ROI) of 0.7 m with a homogeneous nZVI distribution within the domain. The experimental results therefore confirmed that nZVI permeation injection with a good radius of influence is possible in conductive formations. The software MNMs 2023 (Micro- and Nanoparticle transport, filtration, and clogging Model-Suite) was then applied to model the radial transport experiment and extrapolate results with the aim of developing a new graphical tool for simple and effective nZVI permeation injection design. For this purpose, 1800 numerical simulations were performed to build two multiparametric maps to predict the expected ROI in two typical aquifer lithologies and over a wide range of operating conditions.

Comparison of trichloroethylene dechlorination in seawater by sulfidated nanoscale zero-valent iron particles prepared by two methods

Sulfidated nanoscale zero-valent iron (S-nZVI) particles have demonstrated great potential in the remediation of trichloroethylene (TCE) due to their high reactivity and electron selectivity. However, very few studies have been carried out to investigate their application in salinity water or seawater. In this work, two kinds of S-nZVI particles were prepared through different methods including the chemical reduction method (CH-S-nZVI) and the bioprecipitation method (BP-S-nZVI), and then their performances in TCE remediation in seawater environment were thoroughly compared. The results suggested that the TCE removal by CH-S-nZVI particles in seawater is reduced compared to that in fresh water. However, the difference is negligible for BP-S-nZVI particles. It indicates that the seawater has a relatively strong inhibitory effect on the TCE degradation by CH-S-nZVI, but the inhibition for BP-S-nZVI is very weak. Furthermore, this work verified that sodium chloride and organic matters have obvious inhibitory effects on the TCE dichlorination, while coexisting ions such as NO3-, SO42- and Mg2+ are helpful to the degradation of TCE. The research proved that the performance of BP-S-nZVI particles in seawater is superior to CH-S-nZVI particles, providing a suitable candidate for the treatment of polluted aquifers in coastal and near-shore areas.

An ultra-small fluorescence zero-valent iron nanoclusters selectively kill gram-positive bacteria by promoting reactive oxygen species generation

A list of the most dangerous bacteria that are multiple-drug resistance has been published by WHO, among which are various Gram-positive bacteria related with serious healthcare and community-associated infection. An effort is called for developing new strategies to combat the resistance, and nanomaterial-based approaches provide an ideal potential to mitigate the antimicrobial resistance as an alternative to antibiotics. Nanoscale zero-valent iron particles exhibited a good antimicrobial activity by triggering Fenton reaction, however, no zero-valent iron nanoclusters are developed as antimicrobial medical materials. In this work, a novel ultra-small zero-valent iron nanoclusters (usZVIN) was synthesized by one-step reduction in aqueous solutions, which exhibited bright red fluorescence at 616 nm. Interestingly, the usZVIN displayed an excellent selectively antibacterial activity against Gram-positive bacteria, and little effects on Gram-negative bacteria. The killing efficiency of usZVIN against S. aureus can reach 100 % with a concentration of 40 μg mL−1 after 1 h incubation, whereas there is no killing effect of usZVIN against E.coli even with a concentration of 900 μg mL−1 for 4 h. The antimicrobial mechanism of usZVIN was demonstrated to be the intracellular reactive oxygen species (ROS) production triggered by usZVIN due to its excellent peroxidase-like activity. Collectively, our findings suggested that usZVIN is a good medical-material candidate for fighting against Gram-positive bacterial infections, especially when we need leave beneficial Gram-negative bacteria intact.

Assessing the effectiveness of nanoscale zero-valent iron particles produced by green tea for Cr(VI)-contaminated groundwater remediation

Nanoscale zero-valent iron particles (NZVI) produced by using green tea (GT) extract as a reductant can remove Cr(VI) from water effectively, which can be utilized in groundwater remediation. In order to define the reaction mechanism and removal effect in the aquifer, in this study, GT-NZVI particles were prepared and measured by some characterization methods to define their surface performance, and then batch and one-dimensional experiments were carried out to reveal the reaction properties of GT-NZVI and Cr(VI) in groundwater. The results showed that the prepared GT-NZVI particles were regular spherical with a diameter of 10–20 nm, which could disperse in water stably. The main component of GT-NZVI was α-Fe with superficial polyphenols as a stabilizer. GT-NZVI suspension had good ability to reduce the Cr(VI) to Cr(III) in water. When the concentration of GT-NZVI was 1 g/L, the removal efficiency of Cr(VI) with an initial concentration of 100 mg/L reached 92.8% in 1 h reaction. In column tests, GT-NZVI passed through the natural sand column successfully with an average outflow percentage of 71.2%. The simulated in-situ reaction zone (IRZ) with GT-NZVI was used to remediate Cr(VI) contaminated groundwater. The outflow concentration of Cr(VI) kept in 0.14–0.32 mg/L corresponding to the outflow rate below 0.32% within 15 days, and the removal efficiency of Cr(VI) by IRZ with GT-NZVI decreased with the increase of aquifer medium particle size, groundwater flow rate and ionic strength. Most of Cr(III) as reduzate was adsorbed or immobilized on the surface or in the lattice of GT-NZVI, which indicated effective immobilization for chromium.

Iron nitride nanoparticles for rapid dechlorination of mixed chlorinated ethene contamination.

Sulfidation and, more recently, nitriding have been recognized as promising modifications to enhance the selectivity of nanoscale zero-valent iron (nZVI) particles for trichloroethene (TCE). Herein, we investigated the performance of iron nitride (FexN) nanoparticles in the removal of a broader range of chlorinated ethenes (CEs), including tetrachloroethene (PCE), cis-1,2-dichloroethene (cis-DCE), and their mixture with TCE, and compared it to the performance of sulfidated nZVI (S-nZVI) prepared from the same precursor nZVI. Two distinct types of iron nitride (FexN) nanoparticles, containing γ'-Fe4N and ε-Fe2-3N phases, exhibited substantially higher PCE and cis-DCE dechlorination rates compared to S-nZVI. A similar effect was observed with a CE mixture, which was completely dechlorinated by both types of FexN nanoparticles within 10 days, whereas S-nZVI was able to remove only about half of the amount, most of which being TCE. Density functional theory calculations further revealed that the cleavage of the first C-Cl bond was the rate-limiting step for all CEs dechlorinated on the γ'-Fe4N(001) surface, with the reaction barriers of PCE and cis-DCE being 29.9, and 40.8kJmol-1, respectively. FexN nanoparticles proved to be highly effective in the remediation of PCE, cis-DCE, and mixed CE contamination.

Synthesis of Micro-Electrolysis Composite Materials from Blast Furnace Dust and Application into Organic Pollutant Degradation.

A micro-electrolysis material (MEM) was successfully prepared from carbothermal reduction of blast furnace dust (BFD) and coke as raw materials in a nitrogen atmosphere. The MEM prepared from BFD had strong ability in removing methyl orange, methylene blue, and rose bengal (the removal rates of methyl orange and methylene blue were close to 100%). X-ray diffraction showed that the iron mineral in BFD was ferric oxide, which was converted to zero-valent iron after being reduced by calcination. Scanning electron microscopy showed that nano-scale zero-valent iron particles were formed in the MEM. In short, the MEM prepared from BFD can effectively degrade organic pollutants.

Immobilized nanoscale zero-valent iron for synergistic enhanced removal of pentachlorobenzene with Pseudomonas sp. JS100.

Highly chlorinated benzenes usually have a low efficient degradation in environment. Here we proposed a synergistic removal strategy of pentachlorobenzene (PeCB) using Pseudomonas sp. JS100 coupled with immobilized nanoscale zero-valent iron (NZVI). The structural and textural features of the synergistic system were characterized by X-ray powder diffraction, field emission scanning electron microscopy, and a specific surface area and pore size analysis. Nanoscale zero-valent iron particles were dispersed and attached to the biofilter, which increased the specific surface area to 34.5m2g-1. The batch experiment revealed that the removal efficiency of PeCB reached 80.2% in the synergistic system within 48h. The degradation followed pseudo-first-order reaction kinetics, and the reaction rate constant was measured to be 0.0336 h-1. In the degradation mechanism, PeCB was degraded by NZVI to lower chlorobenzenes, which were utilized by Pseudomonas sp. JS100 as nutrients, thereby achieving rapid removal of PeCB.

Arsenic Adsorption on Nanoscale Zerovalent Iron Immobilized on Reduced Graphene Oxide (nZVI/rGO): Experimental and Theoretical Approaches

Arsenic (As) contamination of water and foodstuff has motivated the development of methods to sense, quantify, and/or remediate As contamination in such samples. Nanoscale zero-valent iron (nZVI) particles have recently emerged as a suitable material for adsorbing As. In order to enhance its performance, these nanoparticles were assembled into reduced graphene oxide (rGO) sheets via a direct iron reduction to yield nZVI/rGO materials. Transmission electron microscopy images showed that nZVI particles of 7 nm mean particle size were well dispersed over the rGO sheets. Zeta potential was measured in a pH range from 2 to 12 and showed a point of zero charge at pHpzc 6.5. As adsorption onto nZVI/rGO materials, using 15 ppm As solutions of pH ranging from 3.6 to 7.9, showed that adsorption is better in acidic pH, reaching approximately 80% of As adsorption in 10 min. Density functional theory calculations were carried out to evaluate the As adsorption over nZVI/rGO by using simplified models of magnetite nanoparticles supported on graphene. As bonds to surface oxygen atoms and adsorption are greatly favorable near lattice defects, with adsorption energies between −6.61 and −6.44 eV. After adsorption, As transfers electron density to the surface, resulting in a positive charge of +3.

Polyethyleneimine stabilized nanoscale zero-valent iron-magnetite (Fe3O4@nZVI-PEI) for the enhanced removal of arsenic from acidic aqueous solution: Performance and mechanisms

Nanoscale zero-valent iron (nZVI) particles have a high removal affinity toward arsenic. However, particle agglomeration and surface passivation hinder their practical application in wastewater treatment. Herein, we report the design and synthesis of an economically viable polyethyleneimine stabilized nZVI-magnetite (Fe3O4@nZVI-PEI) that exhibits a fast and efficient removal of arsenic (As(III/V)) from wastewater. Microstructure analyses by SEM and TEM indicated that PEI efficiently minimized particle agglomeration. The higher the point of zero charge (pHpzc) value of Fe3O4@nZVI-PEI (∼9.4) over bare Fe3O4@nZVI (∼8.2) is indicative of the role of PEI in the sorption of the arsenic species. The experimental results showed a removal efficiency of 95.8% for As(III) and 90.5% for As(V) at an optimum pH of 3.0. The adsorption kinetics followed the pseudo-second-order and the equilibrium isotherm data fitted to the Sips model with the superior maximum adsorption capacities of 572.40 mg/g for As(III) and 548.80 mg/g for As(V). FTIR, XRD, and XPS analyses provided insight into the possible adsorption mechanism that arsenic is taken up by generating monodentate and bidentate inner-sphere complexes with -OH, electrostatic interactions with primary amines, and partial oxidation of As(III) to As(V). In contrast to Cl-, NO3-, and SO42-, PO43- showed a significant competitive effect on the sorption of both As(III/V) species. Overall, this work provides a practical and highly efficient approach for arsenic remediation in wastewater and contaminated soils, and simultaneously resolves the stabilization problems of nZVI nanoparticles.

Promotion of ciprofloxacin adsorption from contaminated solutions by oxalate modified nanoscale zerovalent iron particles

• Oxalate addition greatly enhanced the removal of CIP by Fe 0 from 45.04% to 95.74%. • 0.3 g L −1 of Fe 0 , 0.3 mM of oxalate, pH 7, and 25℃ are the optimal removal conditions. • Oxalate addition promoted the adsorption of CIP instead of oxidation by ROS. • The maximum adsorption capacity of CIP by (Fe 0 /oxalate) system is 294.66 mg g −1 . • Oxalate addition significantly reduced the treatment cost from ¥65.72 to ¥29.12. Water contamination by ciprofloxacin (CIP) is a global and emerging issue because it increases the risk of infection by antimicrobial resistant bacteria. CIP removal from water by iron nanoparticles (Fe 0 ) with the presence of oxalate hasn't been reported yet. The present study demonstrated that the addition of oxalate to Fe 0 nanoparticles improved the removal of 100 mg L −1 of CIP from 45.04% to 95.74% under the following optimum conditions: [Fe 0 ] = 0.3 g L −1 , [oxalate] = 0.3 mM, initial pH = 7, and temperature = 25 ℃. Furthermore, the experimental results illustrated that high concentrations of dissolved oxygen in the aqueous solution greatly decreased the removal efficiency of CIP by (Fe 0 /oxalate) system from 97.69% (N 2 atmosphere) to 67.47%. Similarly, the performance of (Fe 0 /oxalate) system declined from 95.43% to 85.23% because of increasing the ionic strength of the solution from 0 to 100 mM. In contrast, the influence of humic acid (0 – 40 mg L −1 ) on the removal of CIP by (Fe 0 /oxalate) system was neglectable. Also, the negative impact of coexisting ions on the competence of (Fe 0 /oxalate) system was in the following order: Mg 2+ > NO 3 – > SO₄ 2- > Ca 2+ > CO 3 2– > K + . In addition, the desorption experiments and the results of SEM-EDS, XRD, and FTIR revealed that physisorption and chemisorption were responsible for CIP removal by (Fe 0 /oxalate) system as the addition of 0.3 mM of oxalate boosted the surface complexation between Fe 0 nanoparticles and the carboxylic, ketone, and piperazinyl groups in CIP. These results were supported by the outcomes of kinetics, isotherm, and thermodynamic analysis. Moreover, oxalate addition significantly reduced the treatment cost of 1 L of 100 mg L −1 of CIP and the generated sludge by approximately 55.68% and 57%, respectively. Finally, this study proved that (Fe 0 /oxalate) system is inexpensive, practical, and more efficient than most of the reported Fe 0 -based systems with a maximum adsorption capacity of 294.66 mg g −1 .

Toxicity of zero-valent iron nanoparticles to soil organisms and the associated defense mechanisms: a review.

Nanoscale zero-valent iron particles (NZVI) are widely used in a variety of industries owing to their advantageous mechanical, physical, and chemical properties. These particles can be released into environmental media, including water, soil, and air, through several pathways. NZVI in the ecosystem can be taken up, excreted and distributed within organisms, which is harmful to plants, animals and humans. Plants play a significant role as producers in the ecological circle and can both positively and negatively affect the ecological behavior of NZVI. Therefore, understanding the relationship between plants and NZVI is likely to be of great value for the assessment of NZVI-associated risks and future research directions. In this review, we summarize the current knowledge on the uptake, distribution, and accumulation of NZVI in plants; the phytotoxicity triggered by NZVI exposure at the physiological, biochemical, and molecular levels; and the defense mechanism used by plants to defend against NZVI-induced insults. We further discuss the toxic effects of NZVI on soil animals and microorganisms as well as the risk posed by the presence of NZVI in the food chain.

Transformation of sulfidized nanoscale zero-valent iron particles and its effects on microbial communities in soil ecosystems

Sulfidized nanoscale zero-valent iron (S-nZVI) is a promising material for in situ soil remediation. However, its transformation (i.e., aging) and effects on the microbial community in soil ecosystems are largely unknown. In this study, S-nZVI having low (S-nZVI (L)) and high sulfur-doping (S-nZVI (H)) were incubated in soil microcosms and bare nZVI was used as a control. Their aged products were characterized using microspectroscopic analyses and the changes in the corresponding soil microbial community were determined using high-throughput sequencing analyses. The results indicate that severe corrosion of both bare and S-nZVI occurred over 56 days of aging with significant morphological and mineral changes. Magnetite, lepidocrocite, and goethite were detected as the main aged products. In addition, sulfate ions, pyrite, and iron polysulfide were formed in the aged products of S-nZVI. Cr(VI) removal test results indicated that S-nZVI(L) achieved the best results after aging, likely because of the optimal FeS arrangement on its nanoparticle surfaces. The presence of nZVI and S-nZVI increased the abundance of some magnetotactic microorganisms and altered bacterial and fungal community structures and compositions. Moreover, the addition of S-nZVI enriched some bacterial and fungal genera related to sulfur cycling because of the presence of sulfide-bearing material. The findings reveal the transformation of S-nZVI during aging and its effects on microbial communities in soil ecosystems, thereby helping to the evaluation of S-nZVI application in soil remediation.

Combat antimicrobial resistance emergence and biofilm formation through nanoscale zero-valent iron particles

The emergence of antimicrobial resistance (AMR) and bacterial biofilm formation in water-related systems (e.g., drinking water distribution pipes) have been posing challenges to public health. Compared to conventional disinfection processes, nanomaterial-based approaches hold promise for mitigating AMR emergence and controlling biofilm formation. In this study, we investigated the performance and mechanisms of nanoscale zero-valent iron (nZVI) and its derivates (carboxymethyl cellulose-nZVI, oxidized or “Aged” nZVI, and Fe3O4 nanoparticles) on preventing AMR emergence and biofilm formation. Results show that the long-term exposure to subminimum inhibitory concentrations of nanoparticles except for Fe3O4 are able to prevent AMR emergence and biofilm formation. Except for Fe3O4, other nZVI nanoparticles are also capable of eradicating pre-established biofilms. The capability of these nanoparticles against AMR and biofilm can be attributed to the overproduction of reactive oxygen species, cell membrane damage and repression of efflux pumps. Collectively, our findings suggest that nZVI nanoparticles are promising alternatives to combat bacterial AMR emergence and biofilm formation in water-related systems.

Removal of Organoselenium from Aqueous Solution by Nanoscale Zerovalent Iron Supported on Granular Activated Carbon

Nanoscale zerovalent iron particles (nZVI) immobilized on coconut shell-based granular activated carbon (GAC) were studied to remove organoselenium from wastewater. A chemical reduction technique that involves the application of sodium borohydride was adopted for the adsorbent preparation. The texture, morphology and chemical composition of the synthesized adsorbents were analyzed with a scanning electron microscope (SEM), nitrogen adsorption–desorption isotherms and X-ray diffraction (XRD). Batch experiment with various pHs and contact times were conducted to evaluate nZVI/GAC adsorption performance. The results showed that nZVI/GAC has a strong affinity to adsorb selenomethionine (SeMet) and selenocysteine (SeCys) from wastewaters. The maximum removal efficiency for the composite (nZVI/GAC) was 99.9% for SeCys and 78.2% for SeMet removal, which was significantly higher than that of nZVI (SeCy, 59.2%; SeMet, 10.8%). The adsorption kinetics were studied by pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models. Amongst the two, PSO seemed to have a better fit (SeCy, R2 > 0.998; SeMet, R2 > 0.999). The adsorption process was investigated using Langmuir and Freundlich isotherm models. Electrostatic attraction played a significant role in the removal of organoselenium by nZVI/GAC adsorption. Overall, the results indicated that GAC-supported nZVI can be considered a promising and efficient technology for removing organoselenium from wastewater.